The invention relates to a closure device, preferably made of plastic, for bags, comprising a male extruded section and a female extruded section, which are connected with film and are adapted to be detachably connected with each other. The invention furthermore relates to a bag, preferably made of plastic, a method for the production of a closure device or a bag and a tool for the production of a closure device or a bag.
Known closure devices for bags of the aforesaid type, which may be co-extruded with the film from a tubular dye, are described in the German patent publication 1,486,627 C and 1,950,724 C. As another example, U.S. Pat. No. 4,263,079 describes a closure device which is extruded from a dye onto prefabricated film. It is also possible to extrude the closure i a device by itself from a dye and then to connect it with a film by welding or bonding.
Heretofore, a principal preoccupation in the art has been to produce closure devices with the smallest possible dimensions, in order to save material and to allow easier transverse welding on bag making machines, since any reinforcement of the closure device part will mean that in later hot cutting, in the course of which bags are produced from the film with the closure, the welding operation will be impeded or additional plant will be called for.
One disadvantage of known closure devices is that the male section or rib (i.e., the projecting hook), can be very readily displaced to the side so that a user who is not familiar with such a closure device or bag will frequently have difficulties when closing the closure device or the bag fitted therewith. It has been seen that such closure devices or bags fitted therewith and which are intended to be reusable so that the contents--more particularly in supermarkets and small stores--may be sealed off, are not always reclosable so that there is a chance of the contents deteriorating simply because the bag has been opened once. It is only seldom the case that a user is able to readily shut the narrow, thin single groove closure devices of the foregoing type.
In the case of the aforesaid known closure devices, the female section which is to accept the male section, is stiffer owing to the necessarily reinforced back so that any attempt to close the known closure device or the bag therewith without starting at one of the edges will simply result in the male section, (i.e., the single hook,) slipping to the side too easily so that an inexperienced user is not able to introduce the single hook precisely into the female section.
The European patent publication 114,373 A describes a design in which the male section is stiffened by having ribs, which extend in the same direction as the male section and are spaced therefrom. The ribs are placed on different sides of the male section and point in the same direction as it does. This closure device suffers from the disadvantage that a substantially greater amount of material is required, this being due to the comparatively large ribs and the additionally required reinforced back. The ribs are essentially of the same size as the male section. These features taken together also have a disadvantageous effect on the costs of production and furthermore are a potential disadvantage for the environment owing to the need to dispose of the closure device when no longer required. Furthermore the production of the tools is more difficult since a relatively complex matching of the respective dyes (i.e., extrusion dyes) is needed.
The European patent publication 223,125 A describes a device in the case of which two fins are arranged on the left and the right of the male section, and which point in the same direction as the male section. However, the thickness of the back of the section is reduced. The fins however mean that substantially more material is required than is the case with the projections as proposed in the present invention. A further drawback with the design in accordance with tile said European patent publication 223,125 A is that upon pressing the two section parts together and running one's fingers along it to close the section, the user will only be able to detect the slightly higher part with his thumb, such higher part being provided under the male section and which is not able to be avoided for rheological reasons. The guiding action for the thumb on closing the section is thus poor.
It is, therefore, an object of the invention is to provide an improved device of the aforesaid type which may be readily closed while being able to be simply and cheaply produced.